Coronary blood flow and distribution in right ventricular hypertrophy.

Myocardial blood flow and distribution in animals with righ ventricular (RV) hypertrophy have not been studied extensively in the experimental laboratory. This study was carried out to investigate whether or not ischemia can be induced in the hypertrophied right ventricle. Ten adult foxhounds underwent banding of the pulmonary artery. One year later coronary flow and distribution were studied by use of radioactive microspheres. Myocardial oxygen supply and demand were estimated by planimetry of aortic and RV pressure tracings. Data were obtained in the control state, during atrial pacing to a heart rate of 200 +/- 4 beats/min (mean +/- SD), during aorta-right atrial shunting to reduce mean aortic pressure to 60 +/- 6mm Hg, and during aortic constriction to produce a mean aortic pressure of 145 +/- 8mm Hg. RV weight/body weight ratio was 2.2 +/- 0.2 gm/kg(normal, 1.3 +/- 0.1 gm/kg) (p less than 0.001). RV free wall thickness was 11.3 +2- 0.7 mm (normal, 6.7 +/- 0.4 mm) (p less than 0.001). At rest, RV oxygen supply/demand ration was 4.7, and the RV subendocardial/subepicardial (Endo/Epi) flow ratio was 0.93. During atrial pacing, RV supply/demand was 54% of control (p less than 0.01), RV Endo/Epi ratio was 1.00 (p less than 0.05), and right coronary artery (RCA) resistance was 59% of control (p less than 0.01). Aorto-right atrial shunting resulted in an RV supply/demand ratio of 31% of control (p less than 0.01), RV Endo/Epi ratio of 0.95, and RCA resistance of 45% of control (p less than 0.01). During aortic constriction, RV supply/demand ratio was 132% of control (p less than 0.05), RV Endo/Epi ratio was 0.92, and RCA resistance was 146% of control (p less than 0.01). Phasic RCA flowmeter tracings demonstrated an increased proportion of diastolic flow in the study animals as compared to normal animals. In conclusion, myocardial blood flow and distribution in the hypertrophied right ventricle remained normal at rest and during hemodynamic stress. Compensatory mechanisms which maintain normal flow and distribution may include changes in RCA resistance and phasic flow patterns. Under the imposed conditions, RV ischemia and failure did not occur.

Evaluation of right atrial-pulmonary artery conduits for tricuspid atresia. Experimental study.

Blood flow through right atrial-pulmonary artery (RA-PA) conduits was investigated. Experiments were designed to evaluate the pumping function of the right atrium, effects of the atrial versus ventricular pacing site, the necessity of a valve within the conduit, and the effect of positive-pressure ventilation on conduit flow. Twenty foxhounds were subjected to silicone patch closure of 90 percent of the tricuspid valve orifices to create stenosis. Ten dogs successfully underwent RA-PA shunting with a conduit with paralled limbs, one containing a prosthetic valve. The proximal main pulmonary artery was ligated to ensure total diversion of blood via the conduit. Valved and nonvalved conduit flow was significantly correlated with right atrial pressure (RAP): r = 0.95, p less than 0.05; r = 0.98, p less than 0.01, respectively. There was no significant effect of increasing heart rate (p = 0.19), atrial versus ventricular rhythm (p = 0.28), or the presence of a valve (p = 0.63). Increasing tidal volume resulted in increasing tidal conduit flow (expiration-inspiration) (r = 1.0, p less than 0.01), but mean flow was unaffected. Therefore, RAP is the most important factor influencing conduit flow. The absence of a valve, ventricular rhythm, and tachycardia did not significantly alter flow in this acute experimental model.

Evaluation of computed tomography in the detection of pulmonary metastases: a prospective study.

Conventional linear x-ray tomography is often used to search for pulmonary metastases but tends to underestimate extent of disease when compared with operative findings. In a prospective study, operative findings were correlated with computed axial tomography and conventional linear tomography performed on 25 patients with a history of extrathoracic malignancy and pulmonary nodules. Computed tomography detected 69 nodules of which 31 proved to be metastases. Conventional linear tomography detected 38 nodules of which 25 were metastases. Of the 54 resected nodules measuring greater than 3 mm, computed tomography detected 42; whereas conventional tomography detected 32. Only six of the 31 additional nodules (20%) detected by computed tomography and not by conventional tomography proved to be metastases. These results suggest that computed tomography is more sensitive than conventional tomography in detecting small pulmonary nodules; however, there is diminished specificity in identifying metastatic nodules.

Prosthetic aortic valves. Indications for and results of reoperation.

During a 15-year period from January 1962 through December 1976, 42 patients who had undergone a previous aortic valve replacement underwent reoperation. The mean interval between operations was 4.4 years. The indications for reoperation were aortic regurgitation resulting from mechanical malfunction (12 patients), ball variance (15 patients), perivalvular leaks (five patients), prosthetic stenosis (eight patients), anemia (one patient), and recurrent emboli (one patient). The indications were characteristic of a specific valve series. The most common reoperation was aortic valve replacement (29/42), which had a 10.3% operative mortality. Poppet change (10/42) carried a 10% operative mortality and no operative deaths followed suture closure of perivalvular leaks. Eighty-eight percent of patients alive six months after reoperation were New York Heart Association functional class 1 or 2. At last follow-up, 95% of surviving patients were still functional class 1 or 2, with a mean cumulative survival of 4.7 years after reoperation. This experience demonstrates that those patients surviving long enough to undergo reoperation can expect a reasonable operative risk, long-term survival, and excellent clinical improvement.

Limits of myocardial protection with potassium cardioplegia.

Preservation of left ventricular function with various potassium-based cardioplegic solutions has been considered to be effective for at least 60 minutes during occlusion of the ascending aorta. The purpose of this study was to define the limits of protection offered by potassium alone. A single bolus of 150 ml of potassium (24 mEq per liter) in normal saline solution at 30 degrees C was injected in the aortic roots of foxhounds at the initiation of periods of 45 minutes, 60 minutes, and 75 minutes of aortic occlusion at a core temperature of 30 degrees C. Data derived from postischemic recovery phase ventricular function curves and force-velocity relations demonstrated excellent protection during 45 minutes of ischemia, inconsistent protection at 60 minutes, and poor protection at 75 minutes.

Continuous epicardial echocardiographic assessment of postoperative left ventricular function.

An ultrasound transducer which is sutured to the heart at operation and removal percutaneously has been developed and tested in 20 animals. The potential of this device to monitor cardiac function was measured by simultaneously recording 67 left ventricular angiograms and echograms over a wide range of hemodynamic function. In addition, the reproducibility of the data obtained from the transducer and the safety of application and withdrawal were examined. We found highly significant (p less than 0.005) linear correlation between echocardiographic and angiographic measurements of left ventricular end-diastolic volume, end-systolic volume, and ejection fraction. This transducer may provide the means to assess left ventricular size and ejection fraction continuously after cardiac operations in man.

Comparison of computed and conventional whole lung tomography in detecting pulmonary nodules: a prospective radiologic-pathologic study.

Whole lung computed tomography (CT) was performed on 25 patients with clinical diagnoses including osteogenic sarcoma. Ewing's sarcoma, rhabdomyosarcoma, fibrosarcoma, and melanoma in whom conventional tomography had revealed from one to four parenchymal nodules in one lung deemed resectable for either staging or treatment purposes. Thoracotomy was performed within 3 weeks after conventional and computed whole lung tomography. All palpable nodules were resected, measured at the time of surgery, mapped by anatomic segment, and submitted for individual histologic evaluation. CT defined more nodules than conventional tomography in 48% of cases. The additional nodules were usually pleural or subpleural and 3--6 mn in diameter. CT identified 78% of all resected nodules greater than 3 mm in diameter, compared to 59% using conventional tomography. CT was also of value in detecting bilateral nodules earlier than conventional tomography and in documenting small nodule growth on successive examination. However, 60% of the additional nodules defined by CT and resected proved to be benign granulomas and pleural-based nodes at thoracotomy.

Effects of coronary-artery bypass on global and regional left ventricular function during exercise.

To determine the effect of coronary revascularization on exercise-induced abnormalities of left ventricular-ejection fraction and regional contraction, we obtained electrocardiograph-gated 99mTc radionuclide cineangiograms before and after operation in 23 consecutive patients. At rest, their average ejection fraction remained unchanged: 51 +/- 3 versus 54 +/- 4 per cent (+/- S.E.M.). However, 17 of the patients showed improvement of ejection fraction during postoperative exercise (increase of 51 per cent). The remaining six patients had no change or a decreased ejection fraction during exercise. All patients with improved ejection fractions during exercise were symptomatically improved. No improvement of regional function occurred at rest, but improvement did occur in regions of exercise-induced dysfunction. Although coronary revascularization has little effect on left ventricular function at rest, the ejection fraction during exercise and exercise-induced wall-motion abnormalities improve in most patients who experience symptomatic improvement.

Vascular access for chronic hemodialysis: use of bovine xenografts to create arteriovenous fistulas.

Adequate vascular access is the hallmark of successful chronic hemodialysis for end-stage renal disease. Between May 1975 and August 1975, it was necessary to use a bovine xenograft in 91 instances to create an arteriovenous fistula for vascular access in patients receiving chronic hemodialysis at the Vanderbilt University Affiliated Hospitals. Forty-two patients had one xenograft, 14 patients had two, and seven had three xenografts. Of all fistulas created with the xenografts, 53% were patent six months after the operation, 36% were patent at 12 months, and 15% have remained patent for 24 months. Thirty-seven percent of the xenografts failed during the first three months after operation. The most common reason for failure was thrombosis of the xenograft. Other complications encountered were false aneurysms, infection of the graft, ischemia of the extremity, and bleeding. Amputation of the lower extremity due to ischemia from septic emboli was necessary in one case. There was no deaths directly related to the use of these xenografts. It is out current opinion that the bovine xenograft should be reserved for use in patients who have had failure of the more conventional type of internal fistula (Cimino type). In selected patients in whom it is not possible to create a Cimino shunt, the xenograft offers adequate primary vascular access.

Selective operative treatment for tetraology of Fallot: rationale and results.

Eighty-one patients with tetralogy of Fallot malformations evaluated between July 1, 1971 and November, 1975 are presented. Fifty-one patients underwent primary intracardiac repair; three died. Twenty-seven patients were corrected after a previous palliative shunt; there was one death. Three additional patients have been palliated and are awaiting repair. While the overall mortality in these patients was less than 5%, the infants undergoing total correction before the age of two years appeared to be at greater risk (25%). There were no deaths in the group of patients undergoing palliative procedures. Based on these data it appears that a safely performed palliative shunt in the symptomatic small infant is a reasonable first step, particularly if the outflow tract of the right ventricle is diffusely hypoplastic.

Surgical treatment of popliteal artery injuries.

Twenty-seven patients with injury to the popliteal artery and associated structures were operated on during the past 15 years. There was no operative or hospital deaths. The limb salvage rate was 56%; the amputation rate was 44%. Those patients with penetrating injuries were found to have a much better salvage rate (85%) than those with blunt trauma (29%). Preoperative arteriography and immediate repair of the popliteal artery by either end-to-end anastomosis or a vein graft is advocated for these patients. Popliteal vein injuries should be repaired when possible by lateral suture or end-to-end anastomosis. Fasciotomy is advocated on a selected basis.

Effect of blood flow rate on subendothelial proliferation in venous autografts used as arterial substitutes.

The effect of augmented and reduced blood flow rates through autogenous vein grafts (AVG) on the histological characteristics of veins used for arterial substitutes was studied in 22 dogs. In each animal autogenous jugular veins were implanted as conduits to replace excised segments of both iliac arteries. In one group (control) blood flow through the AVG conduits was not modified, but in the remaining animals blood flow rate was either augmented by a distal femoral arteriovenous fistula or reduced by a distal arterial stenosis. In the control group in which there was no modification of blood flow, subendothelial proliferative lesions (SEPL) were found in the vein graft, and typical SEPL were found at each anastomosis. However, in those animals in which blood flow was reduced by an average of 44% through the graft, SEPL were more numerous throughout the length of the vein graft, and the anastomotic SEPL were more prominent. In contrast, those animals in which a unilateral distal arteriovenous fistula augmented blood flow through the AVG (average 6.7-fold increase), no SEPL were detected along the length of the graft. Although SEPL were present at the suture lines, the lesions were much less prominent. These findings suggest that the magnitude and distribution of SEPL in AVG are determined, in part, by the rate of blood flow through the graft.

Operative treatment in hypertrophic subaortic stenosis. Techniques, and the results of pre and postoperative assessments in 83 patients.

The results of operative treatment in 83 patients with idiopathic hypertrophic subaortic stenosis (IHSS) are described. Most patients with the disease are asymptomatic, or derive satisfactory symptomatic improvement from nonoperative therapy: administration of propranolol, exerice limitation, control of arrhythmia, etc. Operation is required, however, in 10-15% of patients, those who remain severely symptomatic after nonoperative treatment or who become refractory to it. Operation relieves symptoms in IHSS by relieving obstruction to left ventricular outflow, and for a patient to be considered an operative candidate severe obstruction must be documented at left heart catheterization either under resting conditions or after provocative interventions. All 83 patients were severely incapacitated--58 in Class III and 24 in Class IV. Seventy had obstruction at rest (average gradient 96 mm Hg), and 13 had only provocable obstruction. At operation the hypertrophic interventricular septum was exposed via an aortotomy, and a vertical bar of muscle was resected between parallel myotomy incisions. There were six operative deaths (7%); no patient has died since 1970. Seven patients have died late after operation, five of them from causes unrelated to their heart disease or the operation. All surviving patients describe symptomatic improvement. Fifty-two patients with obstruction at rest preoperatively (average gradient 95 mm Hg) have been studied postoperatively: no resting gradient was evident in 47, while in the remaining five the gradient was less than 25 mm Hg. Recurrence of obstruction has never been observed at late catheterization (21 pts) or late echocardiographic examination (37 pts). Obstruction could not be provoked postoperatively in ten of the 11 patients who had large gradients only with the Valsalva maneuver or isoproterenol administration preoperatively. Obstructed and provocable obstructed patients had similar symptomatic improvement after operation. A variety of rhythm and conduction abnormalities were observed both pre and postoperatively, and these are described in detail. The results of operation in these 83 patients with IHSS demonstrate that gratifying symptomatic and hemodynamic improvement uniformly follows left ventriculomyotomy and myectomy. Relief of obstruction and amelioration of symptoms have proved to be long-lasting during postoperative observation periods extending to 14 years. Continued application of the operative procedure in properly selected patients appears to be indicated.